Problem: Evaluate the following expression when $b = 7$ and $a = 9$. $6$ $b$ $ + 3$ $a$ $ - 5$
Answer: Substitute $7$ for ${b}$ and $9$ for ${a}$ $ = 6{(7)} + 3{(9)} - 5 $ $ = 42 + 27 - 5 $ $ = 64$